Many taxonomic groups of freshwater insects, such as caddisflies, stoneflies, mayflies, dragonflies and damselflies, have a reproductive terrestrial life stage. Some of these are known to
be extremely sensitive to insecticides in the aquatic environment. However, their sensitivity
during the terrestrial adult stage, when they also reproduce, is literally unknown. Consequently, it is also unknown to which extent they are exposed to pesticides during the adult
stage and what effects this may have on population size and structure, both in the short and
long term. So far, risk assessment and management have only focused on avoiding risks to
insect macroinvertebrates in the aquatic environment, and exposure during the terrestrial
stage has been completely neglected. Possible cascading effects on food webs, including effects on fish and birds, also lack in the risk assessment, regardless of whether these result
from pesticide remnants in exposed food or from reduced food sources.
The main objective of the present pilot project has been to investigate whether adult stages of
aquatic insects are sensitive to two insecticides tested in the lab and, if so, to calculate to what
extent realistic exposure may lead to population level effects. The project does not include any
field measurements or investigations of cascade effects on food webs.
For the purpose of investigations, we chose to study the effects of two insecticides on the terrestrial stage of six aquatic insects. The two insecticides were Karate and Confidor, with the
active ingredients lambda-cyhalothrin and imidacloprid, respectively. Listed in Table 4 are the
species we succeeded doing experiments with. Table 4 also gives a summary of experiments
carried out.
